This invention relates to charged particle beam apparatus. More particularly, the present invention relates to improvements in charged particle beam apparatus using a finely focused electron or ion beam such as for example scanning electron microscopes, Auger electron analyzers and ion microscopes and especially, to size reduction of a column containing a charged particle beam generator and a charged particle beam focusing optics of the apparatus.
In the charged particle beam apparatus using a finely focused electron or ion beam such as scanning electron microscope, Auger electron analyzer, ion microscope and secondary ion mass analyzer, a charged particle source of field emission type has hitherto been used widely for the sake of improving resolution. To stably operate the charged particle source of field emission type, however, the interior space of the charged particle source must be maintained at superhigh vacuum condition and to this end, a method has conventionally been employed wherein an evacuation opening is formed directly in the outer wall of vacuum enclosure of a charged particle source of field emission type, a superhigh vacuum pump such as for example an ion pump is connected to the evacuation opening through connection piping and the pump is operated to evacuate the surrounding space of the field emission type charged particle source to a requisite high vacuum (for example, see JP-A-55-148357).
When the aforementioned evacuation method is employed, however, the connection piping has to be arranged exteriorly of the column, thus making the construction of the evacuation system per se complicated and to meet maintenance of necessary evacuation capability, sufficient reduction in size of the connection piping cannot be permitted. If the connection piping is forced to be reduced in size, then the evacuation conductance is decreased and the necessary evacuation capability cannot be obtained. Accordingly, sufficient reduction in size of the overall column structure including the evacuation system for the charged particle source is difficult to achieve.